1. Field of the Invention
The present invention relates to a valve apparatus of a hermetic type compressor, and more particularly to a valve apparatus of a hermetic type compressor capable of easily mounting an exhaust value and a valve spring to an interior of a reentrant groove formed in a cylinder head and reducing the number of elements constituting the valve apparatus to facilitate an the assembly while improving the performance thereof.
2. Description of the Prior Art
When operating a general compressor, a rotor is primarily rotated by the electro-magnetic action of a stator and the rotor upon being supplied with electrical power, and a crank shaft is caused to revolve by the rotation of the rotor.
Then, the vertical rotation force of the crank shaft is converted into a horizontal motion by a connecting rod or slider to horizontally move a piston. Finally, the piston reciprocates within a cylinder.
At this time, while the piston retracts, refrigerant is introduced into the cylinder via a suction inlet and a suction valve of a cylinder head. The refrigerant introduced as above is compressed by the forward movement of the piston to pass through an exhaust hole of the cylinder head, thereby being discharged while opening an exhaust valve.
In designing the conventional valve apparatus of the general hermetic type compressor operated as above, it has been a significant concern for improving efficiency of the compressor to decrease the volume formed within the cylinder and the sum of the internal volume (hereinafter referred to as "dead volume") of the exhaust hole (of which detailed description will be given later) interlocked with the cylinder when the piston linearly reciprocating within the cylinder reaches a top dead center.
This is because the refrigerant gas of high pressure which is left in the dead volume during the discharge process of the compressed gas inflates during the retraction of the piston during the suction stroke of the cylinder to disturb the intake of the refrigerant gas via the suction inlet, so that the efficiency of the compressor is degraded.
The above-mentioned exhaust hole which is formed in the cylinder head communicates with the internal space of the cylinder until the exhaust hole is cut off by the exhaust valve.
The valve apparatus provided between the cylinder and the head cover utilized in the conventional hermetic type compressor relating as above is provided for the intake/discharge of the refrigerant gas into/from the cylinder. Here, the suction valve, cylinder head, packing and exhaust valve are separately formed in a plate type to be sequentially assembled as the valve apparatus; otherwise, a reentrant groove is formed in the cylinder head out of the above elements to install the exhaust valve, etc.
In connection with the description of conventional examples of the valve apparatus having the foregoing two types of the hermetic type compressor, the example of installing the exhaust valve by forming the reentrant groove in the cylinder head will be described with reference to well-known U.S. patents.
As shown in FIG. 1, a valve apparatus of a hermetic type compressor in accordance with U.S. Pat. No. 4,723,896 (hereinafter referred to as a "cited art no. 1") is provided with a reentrant groove 2 in a cylinder head 1 for seating the exhaust valve apparatus.
An exhaust hole 3 is formed to the reentrant groove 2, and an exhaust valve 4 is installed to the upper portion of exhaust hole 3 for closing exhaust hole 3.
A valve spring 5 is installed to the upper side of exhaust valve 4 for repositioning exhaust valve 4 from an open state to the closed state.
The valve spring 5 is joined with a retainer 6 fixed within reentrant groove 2 of cylinder head 1. Also, the above-stated elements are fixed by a clamp 7 installed to the upper side of retainer 6.
The above elements are placed between a head cover 8 and a cylinder 9, and a packing 10 is tightly provided between head cover 8 and cylinder head 1 for preventing a leakage of the refrigerant of high temperature and high pressure.
Undefined reference numeral 9a denotes a piston.
However, the valve apparatus of the hermetic type compressor according to the cited art no. 1 includes a plurality of elements such as exhaust valve 4, valve spring 5 and retainer 6 for fixing these. Consequently, a plurality of elements are required for constituting the valve apparatus, and the slits for insertedly receiving the clamp should be formed in cylinder head 1 to complicate the structure and impede workability.
Furthermore, since valve spring 5 is fixed by using retainer 6, the shape of valve spring 5 is distorted by exhaust valve 4 to deform retainer 6 when distorted valve spring 5 contacts retainer 6. Therefore, respective elements are not properly operated.
Meantime, as shown in FIG. 2, a valve apparatus of a hermetic type compressor in accordance with U.S. Pat. No. 5,209,260 (hereinafter referred to as a "cited art no. 2") includes a suction valve plate 17, a cylinder head 11, an exhaust valve 14, a valve spring 15, a retainer 16 and a head cover 18, which are sequentially coupled to a cylinder (not shown).
Now, shapes of the above-mentioned elements will be described in more detail.
A suction valve 17a and an eject hole 17b are formed around the center of suction valve plate 17.
A reentrant groove 12 formed with a stepped first receiving portion 12a and second receiving portion 12b is formed in one central side of cylinder head 11.
First receiving portion 12a is shaped to be deeper than second receiving portion 12b, and an exhaust hole 13 is formed in the center of first receiving portion 12a.
Then, the exhaust valve 14 and the valve spring 15 are successively seated to one inside of the first receiving portion 12a. Thus, the exhaust valve 14 opens/closes the exhaust hole 13 and valve spring 15 defines the opening/closing range of the exhaust valve 14.
A suction hole 11a which is opened and closed by suction valve 17a of suction valve plate 17 is formed to one outside of the reentrant groove 12.
The retainer 16 is fixedly installed to the second receiving portion 12b shallower than the first receiving portion 12a within the reentrant groove 12 of cylinder head 11 to be disposed to the upper side of the exhaust valve 14 and the valve spring 15, which are sequentially stacked within the reentrant groove 12 in advance.
At this time, the retainer 16 embedded into second receiving portion 12b is so firmly fixed to cylinder head 11 to exclude clamp referred in the above cited art no. 1.
Undefined reference numeral 18 denotes a head cover.
However, the valve apparatus of the hermetic type compressor according to the prior art disclosed in U.S. Pat. No. 5,209,260 has a drawback such that the elements installed within the stepped reentrant groove 12 of cylinder head 11 are small in size but many in number which complicates the assembling operation.
In addition, since the shape of the center of retainer 16 fixed to cylinder head 11 is upwardly deformed by valve spring 15 when the valve apparatus is operated, valve spring 15 is stopped under the state of deviating a prescribed position. As a result, the opening/closing time of exhaust valve 14 cannot be suitably adjusted to cause a backward flowing and great re-expansion loss of the compressed refrigerant, so that the efficiency of the compressor is lowered.
Referring to FIG. 3, a valve apparatus of a hermetic type compressor in accordance with U.S. Pat. No. 5,328,338 (hereinafter referred to as a "cited art No. 3") is formed with a reentrant groove 22 of a predetermined shape in a cylinder head 21 and an exhaust hole 23 within the reentrant groove 22.
A valve installing plane 25 for seating one end of an exhaust valve 24 for opening/closing the exhaust hole 23 is formed to the inside of the cylinder head 21.
A valve spring 26 having an upward inclination for defining the opening/closing range of exhaust valve 24 is provided to the upper side of a exhaust valve 24.
An extension portion 27' of a packing 27 disposed between cylinder head 21 and a head cover 28 is formed to the upper portion of the exhaust valve 24 and valve spring 26, which are sequentially placed within the reentrant groove 22.
An inward projection 30 is formed from an inner side of the head cover 28 toward the upper side of extension portion 27' of packing 27. By this structure, the exhaust valve 24 and one end of the valve spring 26 are fixed in the manner that extension portion 27' of packing 27 is pressed when head cover 28 is assembled with cylinder head 21.
More specifically, in order to fix the exhaust valve 24 and the valve spring 26 for maintaining them in the normal position, extension portion 27' of packing 27 is placed on the exhaust valve 24 and one end of the valve spring 26, i.e., on the end in opposition to a portion of the exhaust valve 24 which covers the exhaust hole 23, to be passively fixed by inward projection 30 formed to the head cover 28.
The cited art no. 3 has a construction that just exhaust valve 24 and valve spring 26 are installed to the reentrant groove 22 formed in cylinder head 21 without installing a retainer. Here, inward projection 30 is formed to head cover 28 to fix valve spring 25.
In the compressor according to the cited art no. 3 constructed as above, the number of elements installed within the reentrant groove 22 is decreased as compared with those of the cited art no. 1, but inward projection 30 is formed to head cover 28 instead for decreasing the elements installed within the reentrant groove 22 to passively fix exhaust valve 24 and valve spring 26.
For this structure, when the valve apparatus is assembled, it is not easy to perform the assembling operation for installing exhaust valve 24 and valve spring 26 within the reentrant groove 22 which is then joined with cylinder head 21 by interposing extension portion 27' of packing 27 to inward portion 30 of head cover 28 to the upper portion of exhaust valve 24 and valve spring 26. Moreover, inward projection 30 must be precisely shaped to accurately assemble head cover 28.
In addition to these, the retainer for defining the ascension of valve spring 26 is not provided to obstruct an efficient fixing of valve spring 26, and the ascension of valve spring 26 is not defined to be unable to restrict the ascending range of valve spring 26, thereby imposing too much stress to the fixing end which fixes valve spring 26.
Consequently, packing 27 pressed by head cover 28 and applied by a force resulting from the repeated ascension of valve spring 26 is easily damaged to make valve spring 26 and exhaust valve 24 not be fixed onto the normal position.
In FIG. 4, another example (hereinafter referred to as a "cited art no. 4") of a valve apparatus of a hermetic type compressor is formed by sequentially assembling a suction valve, a cylinder head, a packing and an exhaust valve, which are shaped as separately-provided plates. Here, a suction valve plate 36, cylinder head 38, an eject valve plate 40, packing 42 and a head cover 44 are successively assembled to be coupled by means of screws 45.
A suction valve 35 of a predetermined shape and an eject hole 36a are formed to suction valve plate 36.
A suction hole 38b and an exhaust hole 38a are respectively formed in cylinder head 38, and a suction hole 40b and an eject valve 41 of a predetermined shape are formed into eject valve plate 40.
Packing 42 is assembled to be interposed where the eject valve plate 40 becomes in contact with head cover 44, thereby preventing a leakage of the compressed gas.
At this time, eject hole 36a in suction valve plate 36 is formed to be opposite to exhaust hole 38a in cylinder head 38 to be communicated with each other.
Also, suction hole 38b of cylinder head 38, suction hole 40b of eject valve plate 40 and suction hole 42b of packing 42 are formed to be opposite to be communicated with one another.
Undefined reference numeral 32 denotes a piston, and reference numeral 33 screws for mounting a cylinder 34.
However, in the valve apparatus of the hermetic type compressor according to the cited art no. 4 described as above, eject hole 36a and exhaust hole 38a formed in suction valve plate 36 and cylinder head 38, which form the valve apparatus in one side of cylinder 34, are bulky which increases the dead volume. Thus, the efficiency of the compressor is degraded.